Device for a radiation plant comprising ray generator and treatment bed



May 21, 1963 Filed July 6, 1959 R. WIDERGE ETAL DEVICE FOR A RADIATION PLANT COMPRISING RAY GENERATOR AND TREATMENT BED 2 Sheets-Sheet 1 INVENTORS BY/BW {10W 291% ATTORNEYS May 21, 1963 Filed July 6, 1959 R. WIDERGE ETAL- DEVICE FOR A RADIATION PLANT COMPRISING RAY GENERATOR AND TREATMENT BED 2 Sheets-Sheet 2 INVENTORS Raff Wderde Hermann Egger /imu {KM/6M A, ADAM ATTORNEY5 3 ,%-,8fi3 Fatented May 21, 1963 inc 3,990,868 DEVICE F012 A RADIATHON PLANT COD/IPRISZWG RAY GENERATGR AND TREATMENT BED Rolf Wideriie, Nussbaurnen, near Baden, and Hermann Egger, Ennetbadcn, Switzerland, assignors to Alrtiengeselischaft Brown, Boyer-i & Cie, Baden, Switzeriand,

a joint-stock company Filed July 6, 1959, Ser. No. 825,015 Claims priority, application Switzerland July 4, 1958 2 Claims. (Cl. 256-91) The invention concerns a device for a radiation plant comprising a ray generator and a treatment bed for irradiating parts of the body of a patient with various angles of incidence for the beam. The source of the rays is rotated by a motor drive about a horizontal axis passing through the ray generator and can be adjusted in the vertical direction by a servomotor. The bed is arranged on a chassis which can be moved on a horizontal track perpendicular to the axis of rotation of the ray producer.

With such a radiation plant it is essential that it is possible to irradiate the body part in question in various ways. It may for instance be necessary to irradiate a certain part of the body from a constantly changing direction whereby the distance between the ray generator and the treatment point should remain constant. The beam axis in this case intersects an imaginary axis in the body, the rotational body axis, about which the beam source apparently rotates. It can, however, also be desired that the position of the irradiated part of the body should vary with the angle of the beam. In this case the beam axis is parallel to the axis of rotation of the body.

According to the invention, this problem is solved by providing the ray generator with an arm which is connected to the treatment bed by means of a pivoted joint, the treatment bed being flexibly supported so as to move in the vertical direction with respect of the track, and a measuring arrangement being provided which determines a vertical movement of the treatment bed relative to the track and produces corresponding control signals, whereby these signals are passed by way of an amplifier to the servomotor for the vertical movement of the ray source, so that the operation of the servomotor is controlled in such a manner that the vertical movement of the treatment bed remains as small as possible.

The invention is explained by means of a constructional example. FIG. 1 shows an irradiation plant where the beam from the ray generator is directed vertically downwards. FIG. 2 shows the same apparatus where the beam is inclined to the point that has to be irradiated.

In FIG. 1 reference numeral 1 indicates the ray generator. The ray generator 1 may be one such as taught in the prior art for radiation thereapy such, for example,

as disclosed in United States Patent No. 2,822,478 granted February 4, 1958 to Rolf Wideroe. The arrow 2 shows the direction of the beam as it leaves the generator. The chassis 3 is equipped with wheels 6 which can roll along a horizontal track 5. The treatment table 4 is mounted on the chassis, so that both the chassis and the treatment bed execute the same horizontal movements.

The ray generator is fixed to the vertical support 8 in a rotatable manner by means of a pivot 7. The tilting movement is produced by means of a reversible drive including a worm wheel 9 secured upon pivot shaft 7 which is meshed with a worm 9a actuated by motor 19. This motor is of the non-synchronous type and causes the ray generator to execute an oscillating movement at a constant angular speed. Switches 39, 31 shown in FIG. 2., are provided at the end positions of the ray generator by means of which the driving motor 10 is rapidly reversed. These end switches 30, 31 and their connections are shown only schematically and operate in a conventional manner to effect periodic reversal of the motor 10. A typical arrangement of such end switches and their manner of operation can be found in United States Patent No. 1,425,- 890 issued August 15, 1922, to W. L. Merrill.

In addition to the oscillating movement, the ray generator can also be adjusted in the vertical direction by means of a servomotor 11 and a vertical guide system. For this purpose the vertical support 8 is fixed to transverse beam 12 which is provided with threaded holes and is supported by the screw spindles 13. When these spindles are rotated, the transverse beam 12 and thus also the ray generator are raised or lowered. These spindles are rotated by way of the gears 14 and motor 11.

In accordance with the invention, ray generator 1 is provided with an arm 15 arranged in the beam direction as indicated by the arrow 2 and having a pivoted joint 16 at its lower end, the joint 16 having a horizontal axis parallel to the pivot shaft 7 of the ray generator 1. This joint 16 is connected by way of the frame 17 with the chassis 3 and is thus also rigidly connected with the treatment bed 4. Each movement of the joint 16 in the horizontal direction corresponds to a similar horizontal movement of the treatment bed. By means of a guide device any tendency for the chassis to tilt due to the lateral force exerted by the arm is prevented. The distance between the beam axis and the rotational body axis determined by the pivoted joint 16 is thus kept constant. When this distance is made equal to zero, during the irradiation process a part of the body lying in the body axis will be irradiated with every beam direction.

For this movement the speed of motor 11 must be maintained at a value which enables the treatment bed to be moved as required without difiiculty. The pivoted joint 16 should not be subjected to a force component which causes the chassis to be raised or lowered. For this pur pose the treatment bed is supported in a vertically flexible manner with respect to the track. The wheels 6 are springsupported by means of the springs 24 which due to their resilience compensate any strong vertical forces which occur. At the same time this resilience is utilized to produce control signals by means of which the speed of motor 11 is regulated.

A measuring arrangement is provided on the chassis for the control system whereby a vertical displacement of the treatment bed or the chassis relative to the track is determined and corresponding control signals are produced. These control signals are amplified in an amplifier 19 and supplied to the servomotor 11 for controlling the vertical movement of the ray generator. The control system operates in such a manner that the speed of the servomotor is so regulated that the vertical movement of the treatment bed is reduced and kept as small as possible.

A roller 20 serves as the measuring element for determining the undesirable vertical movement, this roller being mounted on a vertically arranged rack 21 on the chassis. This rack is in engagement with a gearwheel 22 which carries the moveable part such as the contact arm 23a of a regulating device, for instance a regulating resistor 23. Depending upon whether the arm 15 acts on the chassis in the upward or downward direction, the contact arm 23a of the resistor 23 will be displaced up or down on resis tor 23 as a result of rotation of gear 22 with a corresponding transmission ratio so that control signals derived from the position of contact arm 23a pass to the amplifier input, and the amplifier output is fed to the motor 11 which is influenced correspondingly in the forward or reverse direction with the result that the heighth of the pivoted joint above the track and thus also that of the treatment point above the track is maintained practically constant.

In order to ensure that for each tilted position of the ray generator the beam axis is directed towards a definite point, it is necessary that the beam axis should intersect the extended axis at the pivoted joint 16.

In certain cases it may be desirable that the beam axis should be allowed to pass alongside the joint axis. It may also be expedient to make the arm 15 adjustable as regards its length so that the distance between joint 16 and the axis of rotation 7 can be varied as desired.

We claim:

1. Apparatus for radiation therapy comprising a support, a ray generator producing a beam of rays and mounted on said support for pivotal movement about a horizontal axis, a motor efiecting oscillation of said ray generator about its pivotal axis, means mounting said support for raising and lowering movement in a plane perpendicular to the pivotal axis of said ray generator, a reversible servo motor for raising and lowering said support and said ray generator, a chassis under said ray generator movable along a trackway transverse to the pivotal axis of said ray generator, said chassis including a treatment bed for patients to be treated by said ray generator and towards which the radiation from said ray generator is directed, an arm depending from said ray generator in a direction parallel to the axis of the beam of rays emanating from said ray generator, the lower end of said arm being articulated to said chassis by a pivotal joint with a horizontal axis parallel to the pivotal axis of said ray generator whereby pivotal oscillatory movement of said ray generator accompanied by vertical up and down movement of said support therefor causes said chassis to be moved back and forth along said trackway, means resiliently mounting said chassis and bed for resilient movement in a vertical plane, means producing a variable control signal determined by the departure in height of said bed from a desired central position, and an amplifier to which said control signal is connected as input, the output from said amplifier being connected to said second reversible servo motor for varying the operating speed and direction thereof for raising and lowering said support in accordance with said control signal to maintain said bed at said desired centralposition when said ray generator is oscillated about its pivotal axis by said first motor.

2. Apparatus for radiation therapy as defined in claim 1 where the axis of the radiation beam from said ray generator intersects an extension of the axis of articulation at the lower end of said arm.

References Qited in the file of this patent UNITEDSTATES PATENTS 2,781,454 Green et a1 Feb. 12, 1957 2,793,296 Peterson May 21, 1957 2,822,478 Widere Feb. 4, 1958 

1. APPARATUS FOR RADIATION THERAPY COMPRISING A SUPPORT, A RAY GENERATOR PRODUCING A BEAM OF RAYS AND MOUNTED ON SAID SUPPORT FOR PIVOTAL MOVEMENT ABOUT A HORIZONTAL AXIS, A MOTOR EFFECTING OSCILLATION OF SAID RAY GENERATOR ABOUT ITS PIVOTAL AXIS, MEANS MOUNTING SAID SUPPORT FOR RAISING AND LOWERING MOVEMENT IN A PLANE PERPENDICULAR TO THE PIVOTAL AXIS OF SAID RAY GENERATOR, A REVERSIBLE SERVO MOTOR FOR RAISING AND LOWERING SAID SUPPORT AND SAID RAY GENERATOR, A CHASSIS UNDER SAID RAY GENERATOR MOVABLE ALONG A TRACKWAY TRANSVERSE TO THE PIVOTAL AXIS OF SAID RAY GENERATOR, SAID CHASSIS INCLUDING A TREATMENT BED FOR PATIENTS TO BE TREATED BY SAID RAY GENERATOR AND TOWARDS WHICH THE RADIATION FROM SAID RAY GENERATOR IS DIRECTED, AN ARM DEPENDING FROM SAID RAY GENERATOR IN A DIRECTION PARALLEL TO THE AXIS OF THE BEAM OF RAYS EMANATING FROM SAID RAY GENERATOR, THE LOWER END OF SAID ARM BEING ARTICULATED TO SAID CHASSIS BY A PIVOTAL JOINT WITH A HORIZONTAL AXIS PARALLEL TO THE PIVOTAL AXIS OF SAID RAY GENERATOR WHEREBY PIVOTAL OSCILLATORY MOVEMENT OF SAID RAY GENERATOR ACCOMPANIED BY VERTICAL UP AND DOWN MOVEMENT OF SAID SUPPORT THEREFOR CAUSES SAID CHASSIS TO BE MOVED BACK AND FORTH ALONG SAID TRACKWAY, MEANS RESILIENTLY MOUNTING SAID CHASSIS AND BED FOR RESILIENT MOVEMENT IN A VERTICAL PLANE, MEANS PRODUCING A VARIABLE CONTROL SIGNAL DETERMINED BY THE DEPARTURE IN HEIGHT OF SAID BED FROM A DESIRED CENTRAL POSITION, AND AN AMPLIFIER TO WHICH SAID CONTROL SIGNAL IS CONNECTED AS INPUT, THE OUTPUT FROM SAID AMPLIFIER BEING CONNECTED TO SAID SECOND REVERSIBLE SERVO MOTOR FOR VARYING THE OPERATING SPEED AND DIRECTION THEREOF FOR RAISING AND LOWERING SAID SUPPORT IN ACCORDANCE WITH SAID CONTROL SIGNAL TO MAINTAIN SAID BED AT SAID DESIRED CENTRAL POSITION WHEN SAID RAY GENERATOR IS OSCILLATED ABOUT ITS PIVOTAL AXIS BY SAID FIRST MOTOR. 